1. Field of the Invention
The present invention is directed to a method of processing thick wafers and the resultant products, more particularly to lithographic processing and separating of thick wafers.
2. Description of Related Art
Automated semiconductor processing equipment has been designed for wafer thicknesses generally on the order of 0.5 mm-1.5 mm. Some classes of semiconductor processing equipment are even more limited. The chucks used to support the wafers in the stepper are of a fixed thickness. The chucks could be thinned to accommodate thicker wafers, but this results in a less rigid chuck and could compromise performance. Also, the chucks may only be thinned so far.
When thick wafers, i.e., those having thicknesses not accommodated by current processing equipment, e.g., on the order of 2 mm or thicker, are to be processed, the automated semiconductor processing equipment could be redesigned to allow such processing. However, this redesign will most likely compromise current performance and/or require significant tool modifications. Further, each time a greater thickness is desired, further redesign would be required.
Even once thick wafers have the desired features formed thereon, there are other problems in vertically separating the thick wafers to produce the individual parts. This separation is required to realize the mass production advantages offered by wafer level processing.
The present invention is therefore directed to a method of processing thick wafers, including separating them into individual components, and the resultant structures which substantially overcomes one or more of the problems due to the limitations and disadvantages of the related art.
At least one of the above and other objects may be realized by providing a method of vertically separating a thick wafer having a top surface and a bottom surface, the thick wafer being on a dice support. The method includes aligning a first dicing tool for a first dice with the thick wafer adjacent to the top surface, dicing the thick wafer to create a first dice, flipping the thick wafer so that the top surface is in contact with the dice support, aligning a second dicing tool for a second dice with the composite wafer adjacent to the bottom surface of the thick wafer, and dicing through the thick wafer.
The first and second dicing tools may be the same. After dicing to create the first dice, another wafer may be bonded on top of the first dice. After dicing to create the first dice, a third dicing tool for a third dice may be aligned with the thick wafer adjacent to the another wafer and dicing to create a third dice. The third dice may be created before the second dice. At least two of the first, second and third dicing tools are the same. The aligning may include aligning the second dicing tool through the thick wafer to the first dice an/or to alignment marks on the thick wafer. Alignment marks on the top and bottom surfaces of the thick wafer may be formed prior to aligning the first dicing tool.
The thick wafer may include a first wafer and a second wafer, and these may have different thicknesses and/or be of different materials. At least one of the first and second wafers may be lithographically processed on a wafer level. At least one of the first and second wafers may have a lithographically created optical element thereon. The first and second wafers may be bonded together before aligning of the first dicing tool. The bonding may include providing adhesive material between the first and second wafers, fusing the first and second wafers together, and provide metal pads between the first and second wafers. Before the bonding, at least one of the first and second wafers may be lithographically processed, which may include creating an optical element.
These and other objects of the present invention will become more readily apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating the preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.